Multiple zone heating system



July 4, 1967 H. L.; SMITH, Jr 3,329,344

MULTIPLE ZONE HEATING SYSTEM Filed Aug. 25, 1966 4 Sheets-Sheet l FIG IBF/G. M l

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ATTORNEY July 4, 1967 H, 1 sMlTHl JR 3,329,344,A

MULTIPLE ZONE HEATING SYSTEM 4 Sheets-Sheet Filed Aug. 23, 1966 IG. 7B

INVENTOR. HORACE L. sfu/TH, JR. BY

July 4, 1967 H.1 SMITH, .1R

MULTIPLE ZNE HEATING SYSTEM 4 Sheets-Sheet 5 Filed Aug.

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July 4, 1967 sMrrH, JR 3,329,344

MULTIPLE ZONE HEATING SYSTEM 4 Sheets-Sheet 4- Filed Aug. 23, 1966 JN VEN TOR.. HORACE L. SMITH, Jl?.

United States Patent O 3,329,344 MULTIPLE ZONE HEATING SYSTEM Horace L.Smith, Jr., Richmond, Va., assignor to Hupp Corporation, Cleveland,Ohio, a corporation of Virginia Filed Aug. 23, 1%6, Ser. No. 574,398Claims. (Cl. 237-8) This invention relates to heating systems and, moreparticularly, to novel, improved heating systems of the circulatingliquid type.

The hea-ting systems disclosed herein are specifically intended toemploy eutectic mixtures of inorganic salts in molten form as heattransfer liquids. These mixtures make extremely desirable heat transferliquids since they can @be heated to temperatures in the range of100G-1050" F. without deterioration. The importance of high temperaturesbecomes apparent when it is recognized that a radiator heated to l050 F.will emit four times as much radiant energy per square foot of emittingsurface per hour as one heated to 600 F., which is the maximum practicaltempera-ture attainable by other heat transfer liquids. Moreover, molteneutectic salt mixtures are noncorrosive and nontoxic and are circulatedin liquid form so that they exert no vapor pressure on the system inwhich they are incorporated. Accordingly, they may be used withou-ttaking elaborate precautions against corrosion, t-oxication, or burstingof system components.

Components for heating, handling and circulating these media have beendeveloped; and systems employing t-hem are in use in a few specificspecialized areas. They are not, however, in general use. This isbecause most heating systems in which they could be advantageouslyemployed must be capable of supplying the heat transfer medium toseveral load centers or zones at different temperatures so that varioustemperature requirements may be met in the different centers or zones.Moreover, this must be accomplished with a central or common fluidheating unit as the provision of a separate fluid heater for each zoneor lload center is not economically feasible.

In systems employing more conventional heat transfer media such as hotwater and steam zonal temperature control is readily accomplished byemploying suitable control valves to direct and regulate the flow of theheat transfer medium. However, control valves suitable for this purposehave internal components such as packings and seals for which there areno known materials capable of withstanding the 1000 F. or higherltemperatures attainable by molten eutectic salt mixtures. Accordingly,conventional control techniques cannot be used in systems employing suchmedia.

However, I have now invented a novel arrangement for independentlycontrolling the temperature of a molten eutectic mixture delivered toeach of the several zones of a multizone heating system which does notemploy conventional control valves to regulate and direct the flow ofthe circulating heat transfer liquid and which fulfills the requirementthat all of the liquid for the system be heated by a common heatingunit.

In my novel system, a central heating unit is employed to maintain areservoir of the molten eutectic mixture at a given temperature level.The liquid for each of the heat using centers or zones is drawn from aseparate compartment or chamber in the reservoir into which liquid canflow from the main body of liquid in the reservoir. The temperature ofthe liquid withdrawn from the compartmentalized chamber for each zone isindependently regulated by returning to and mixing withV the relativelyhot liquid flowing into the chamber from the main body of liquid aselectively variable proportion of the relatively cooler liquiddischarged from the associated zone or load center of the heat using endof the system.

By respectively increasing and decreasing the propor- "ice tion ofcooler returning liquid to hot liquid from the main body in thereservoir, the temperature of the liquid delivered to the zone suppliedfrom each compartmentalized chamber can be lowered or raised to meet thetemperature requirements of the zone. Diversion of varying proportionsof the liquid discharged from each zone or load center into theassociated compartmentalized chamber in the reservoir can be readilyaccomplished by any of several simple packingand seal-free mechanicalflow proportioning arrangements regulated by controllers which havesensors in and therefore respond to the temperature in the load centersor zones.

From the foregoing, it will =be apparent that one important primaryobject of the present invention is the provision of multizone heatingsystems employing high temperature circulating heat transfer media andprovided with controls for independently regulating the temperature ofthe liquid supplied-to each of the heat using zones.

Other important, but more specific objects of the present inventioninclude the provision of heating systems as described in the precedingobject:

(l) Which employ heat transfer -media that are solids at normal ambienttemperatures and which include an auxiliary heating system for meltingthe solid media when the system is started up;

(2) In which Ithe control arrangement for regulating the temperature ofthe heat transfer medium supplied to each of the heat using zones orload centers includes an arrangement for mixing a selectively variableproportion of the relatively cool liquid returned from the zone or loadcenter with liquid drawn from a reservoir of relatively hot liquidmaintained at a generally uniform temperature;

(3) In which the control arrangement for regulating the temperature ofthe heat transfer medium is free of packings, seals, and othercomponents which are not capable of withstanding high temperature;

(4) In w-hich the aforesaid control arrangement is simple, reliable, andinexpensive to manufacture and service.

Additional objects, further novel features, and other advantages of thepresent invention will be apparent from the appended claims and as theensuing detailed description and discussion proceeds in conjunction withthe accompanying drawing, in which:

FIGURE l shows the relationship of FIGURES lA and 1B which, together,constitute a generally diagrammatic illustration of a multiple zone or`load heating installation constructed in accord with the principles ofthe present invention;

FIGURE 2 is a section through a heat exchange unit incorporated in amultiple zone heat user in the heating installation of FIGURE l;

FIGURE 3 is a section through the heat exchange unit to a reduced scale,taken substantially along line 3 3 of FIGURE 2;

FIGURE 4 is a partial, partly sectioned plan view of heat transfer fluidheating and storage units incorporated in the heating installation ofFIGURE `l;

FIGURE 5 is a partly sectioned diagrammatic side view of a second,exemplary form of ow divider which may be used in hea-ting installationsconstructed in accord with the principles of the present invention;

FIGURE 6 is a partly sectioned, diagrammatic front View of the flowdivider of FIG. 5:

FIGURE 7 is a view similar to FIGURE 5 of a third, exemplary form offlow divider which may be used in heating installations constructed inaccord with the principles of the present invention; and

FIGURES is a partly sectioned, diagrammatic front view of the flowdivider of FIGURE 7.

Referring now to the drawing, FIGURES lA and 1B depict a multiple zoneheating installation 20 constructed in accord with the principles of thepresent invention and including my novel arrangement for independentlyregulating the temperature of a circulating heat transfer liquidsupplied to each of the several zones of a multiple zone heat using unit22 in the installation.

The illustrated heat using unit 22 is a multiple pass vertical dryer.This dryer, which is exemplary of the multiple zone heat using unitswith which the present invention may be advantageously employed,includes a plurality of rotatably supported rolls 24 arranged in upperand lower rows 26 and 28. The rolls in upper row 26 are directly abovethe spaces y.between the rolls in lower row 28 to direct a web 30 ofproduct to be treated through the, dryer in a plurality of parallel,spaced apart passes or zones 32A-D extending between the two rows ofrolls. As the web of product 30l moves through dryer 22, it is dried andevolved volatiles are carried away from it by fluid supply-return andradiantv heating units 34 and 36 oriented adjacent and parallel topasses 32.

Referring now to FIGURES 1B, 2, and 3, each of the fluid supply-returnand radiant heating units 34 incorporated in dryer 22 includes elongatedmain supply and return ducts 38 and 40 separated by a common dividingwall 41. Branch supply and return ducts 42 and 44 extend transverselyacross the main supply and return ducts, the arrangement of thesecomponents on both sides of the main duct pairs being identical. Asshown in FIGURE 2, the main and branch ducts are integral, the commonwalls 46 of the main ducts forming the bottom walls for the branchducts. Pairs of branch supply ducts are alternated with pairs of branchreturn ducts, and the branch ducts are arranged with their side Walls inabutting relationship.

Branch supply ducts 42 communicate with main supply ducts 38 throughapertures 48 (see FIGURE 2) in the com-mon wall 46 between the main andbranch ducts adjacent the wall 41 separating the main supply and returnducts. Branch return ducts 44 similarly communicate with main returnduct 40` through apertures 50 in common Wall 46 0n the side of commonpartition 41 opposite apertures 48.

Air or other treating fluid is accelerated and directed normally at highvelocity (typically on the order of 2,000- 15,000 feet per minute)against web 30 by nozzles 52 xed to the exterior wall 54 of each branchsupply duct 42. The nozzle inlets communicate with the interior of theduct through apertures 56 in exterior branch duct wall 54. The treatingfluid exiting from nozzles 52 contacts the surfaces of web 30` at highvelocity, scouring away from the surfaces volatiles evolved from theweb. The spent fluid, together with its burden of evolved volatiles,flows into branch return ducts 44 through inlet apertures 58 formed inexterior wall 54.

Units 34 also include radiant heaters 62 as shown in FIGURES 1B, 2, and3. Each heater has a plurality of parallel, spaced apart, straighttubular legs 64 having coplanar centerlines and extending in the samedirection as branch ducts 42 and 44. The legs 64 are connected bytubular end bends 66 alternately located at opposite ends of the heater.The rows of nozzles 52 and exhaust apertures 56 are disposed betweenadjacent legs 64 of the radiant heater.

Units 36, which are located outside the outermost passes 32A and D, maybe identical to units 34 except that there are branch supply and returnducts and their associated supply nozzles and exhaust openings only onone side of the main ducts of these units.

Units of the type discussed above are described in more detail in mycopending application No. 537,132, filed Mar. 24, 1966, for Apparatusand System (which has been abandoned) to which reference may be had ifdeemed necessary for a more complete understanding of the presentinvention.

The treating iluid is supplied to the main supply duct 38 in each unit34 and 36 by a blower 68 connected l through a duct 70 to a uid heater72 incorporated in a fluid heating system (not otherwise shown), whichmay be of the type disclosed in application No. 537,132, if desired.From fluid heater 72, the treating fluid flows through a syste-m supplyduct 74 into the main supply ducts 38 of units 34 and 36.

The spent treating uid and its burden of evolved volatiles flows frombranch return ducts 44 of units 34 and 36 into the associated unit mainreturn ducts 40. From these ducts, the spent Huid and its burden flowsinto system return duct 76.

Main system return duct 7 6 is preferably connected to the inlet ofblower 68 so that the spent treating fluid ma" be recirculated throughthe system. This eliminates the loss of sensible heat which would resultif the spent uid were discharged from the system.

In many applications of the present invention, such as in the drying ofpaper, the percentage of moisture or other volatiles in the treatingduid must be closely controlled to produce the desired characteristicsin the treated product. To permit such control, main system return duct76 is provided with a make-up duct 7S; and a vent duct 80 is located inthe duct 70 between blower 68 and fluid heater 72. Valves 82 and 84control the flow through make-up and vent ducts 78 and 80, respectively.Valves 82 and 84 may be adjusted manually or, if desired, may beautomatically controlled as disclosed in my U.S. Patent No. 3,208,158issued Sept. 28, 1965, for Dryers.

Radiant heaters `62 are heated to operating temperature by circulatingthrough them a heated, liquid heat transfer medium such as HTS. HTS is aeutectic mixture of inorganic salts having a melting point ofapproximately 288 F.

Most commonly, HTS is formulated of 40% sodium nitrite, 7% sodiumnitrate, and 53% potassium nitrate. HTS of this compoistion is marketedby Du Pont as Hitec, by American Cyanamid as Aeroheat 300, and byAmerican Hydrotherm as Hydrotherm 1200. Variations of the abovecomposition include the commercially available HTS mixture of 55%potassium nitrate and 45% sodium nitrate. The physical characteristicsof HTS are discussed in detail in an article by I-I. P. Voznick et al.entitled Molten Salt for Heat Transfer in the May 27, 1963, issue ofChemical IEngineering to which reference may be had if desired.

The primary advantage of using HTS as a circulating heat transferliquid4 is that it may be circulated at extremely high temper-atures (upto 1050 F.) in liquid form. Consequently, the radiant heaters may beheated to heretofore unobtainable temperatures; and yet the systemcomponents need be designed to withstand only very low pressures becauseliquid HTS has negligible Vapor pressure.

Also, unlike high boiling point hydrocarbons and other organic heattransfer mediums, HTS is stable, does not foul, and has superior thermalproperties. In contrast to the heat transfer metals, it is safe,nontoxic7 and has both low corrosion rates and low inventory costs.Moreover, HTS has an excellent thermal carrying capacity and isrelatively inexpensive.

Referring now primarily to FIGURES 1A and 4, one of the most importantfeatures of the present linvention is the no-vel system provided forheating the liquid medium, circulating it through the radiators 62 inthe several zones `or passes 32 of dryer 22, and independentlycontrolling the temperature of the radiators 62 in each of the dryerzones. This system includes as major components a liquid heating unit86, a storage tank 88 for the heated liquid, a zone circulation andcontrol system 90 for each of the dryer zones 32, and an auxiliarysystem including a heating unit 92 for melting the HTS when theinstallation is started up.

Liquid heating unit 86, which may be of any desired construction, isconnected to storage tank SS by supply and return conduits 94 and 96. Apump 98 in storage tank 88 and connected to the inlet of return conduit96 circulates heat transfer liquid from the storage tank through theheating unit and back to the storage tank. Suitable conventionalcontrols (not shown) are provided to so regulate the operation ofheating unit 86 that it will maintain the heated liquid in the storagetank at a constant, preselected temperature. Storage tank 88 thereforeconstitutes a reservoir from which heat transfer liquid at the selectedtemperature may be withdrawn and circulated through dryer zones 32A-D tomaintain the radiators 62 in the latter at operating temperature.

Referring still to FIGURE 1A, each of the zone circulating and controlsystems provided for this purpose includes an individual compartment orchamber 100 within the main storage tank 88. Each compartment 100communicates with the main body of liquid 102 in the storage tankthrough a weir 104. Therefore, if the liquid level in a compartment 100falls below the level of liquid body 102, liquid will flow into thecompartment through its weir 104, tending to restore the liquid level inthe compartment to the level of liquid body 102.

Insulation 105 surrounding each compartment or tank 100 thermallyisolates the liquid in the compartment from the main body of liquid 102.This permits the liquid in the compartments to be maintained attemper-atures different from that of the liquid in main body 102.

Referring now to both FIGURES lA and 1B, heat transfer liquid iscirculated from compartment 100 of the associated circulation andcontrol system 90 to the radiators 62 in dryer zone 32a through a mainzone supply conduit 106 and branch zone supply conduits 108 by a zonepump 110 in the compartment. After circulating through the radiators,the liquid, now at a lower temperature, flows through branch returnconduits 112 and main zone return conduit 114 to a flow proportioningcontrol 116. Control 116 regulates the temperature of the heat transferliquid supplied from compartment 100 to zone 32A.

As shown in FIGURES 1A and 4, flow proportioning control 116 includes atrough or bucket 118 pivotally mounted 'on rods or pins 120 abovecompartment side wall 122. Rectangular openings 124 and 125 in bucket118 discharge the liquid returned from radiators 62 in zone 32A tobucket 118 into compartment 100 'and into the main body of liquid 102 instorage tank 88, respectively.

Bucket 118 is connected through a link 126 to the piston 127 of apneumatic or hydraulic motor 128 (see FIGURE 1A). The operation of motor128 is regulated by a temperature responsive controller 130 having asensor 132 in contact with one of the radiators 62 in zone 32A.

Assuming first that the radia-tor temperature in zone 32A drops belowthat which it is desired to maintain, controller 130 will pivot bucket118 to the position shown for the bucket in the controller of zone 32B.With bucket 118 thus positioned, all of the liquid returned from dryer22 will be discharged into the main body of liquid 102 in storage tank88. Since liquid is being continuously Withdrawn from compartment 100 byzone pump 110, this will cause a drop in the liquid level in compartment100. Accordingly, relatively hot liquid will flow into compartment 100through opening 104. This increases the temperature of the liquid incompartment 100 and, accordingly, the temperature of the liquid suppliedto the radiators 62 in zone 32A, raising the temperature of the latter.In actual practice the compartments 100 Would contain baflling or otherappropriate structure to effect an intimate mixing of the liquid flowinginto the compartment and thereby maintain all of the liquid in thecompartment at a uniform temperature.

As the temperature of the radiators in zone 32A approaches the desiredtemperature, temperature controller' 130, acting through motor 128,shifts bucket 118 toward the illustrated position. With the bucketmoving toward this position, an increasing proportion of the liquiddischarged from dryer 22 is diverted into compartment 100 and adecreasing proportion into the main body of liquid 102. This decreasesthe temperature of the liquid in compartment due to the reducedproportion of hot liquid flowing into the compartment from main body102. Thus, the rate of increase of the temperature of radiators 62 isreduced as they approach the desired temperature.

With a constant heat load in zone 32A and the radiators 62 in this zoneat the desired temperature, bucket 118 will be positioned so that theproportions of the liquid owing into the tank from bucket 118 and fromthe main body of liquid 102 will maintain the temperature in the zone atthe desired level.

The function of proportioning control 116 is simi-lar if the temperatureof the radiators 62 in zone 32A rises above the desired level because ofa decreasing heat load in zone 32A or other reason. In this event,temperature controller 130, acting through motor 128, shifts bucket 118toward the position of the bucket of the controller for zone 32C. Thisincreases the volume of relatively cool liquid discharged intocompartment 100 and decreases the volume of hotter liquid flowing intocompartment 100 through Weir 104 from the main body of liquid'102 instorage tank 88. This lowers the temperature of the liquid incompartment 100 available for supply to zone 32A, reducing thetemperature of the liquid supplied to the zone in response to thedecreasing heat load to maintain the radiator 62 in the zone at thedesired temperature.

The foregoing description of the operation of flow proportioningcontrollers 116 assumed that the temperature of the radiators in thezones was to be maintained constant. Controllers 116 are not limited tothis mode of control, however. For example, it may be desirable toregulate the temperature of the radiators by the speed of the web 30moving through dryer 22, the temperature of the radiators beingincreased as the web speed increases. Temperature controllers may bereadily programmed to effect this mode of operation; or the same resultmay be accomplished by making controllers 130 responsive to the speed ofthe web rather than radiator temperature. In short, with only minormodifications which will be obvious to those skilled in the controlarts, flow proportioning control 116 may be made to respond to any oneof several parameters or to various combinations of such parameters.

When heating installation 20 is shut down, the buckets may be emptied byshifting them to the position of the bucket in the controller for zone32C. This eliminates the need for an auxiliary heating system to meltHTS in the buckets when the system is started up.

The novel control arrangement just described, which is duplicated forzones 32B-D, is an important feature of the present invention since,heretofore, there was no Way of providing independent zone control insystems employing HTS or similar fluids as heat transfer media. Asindicated above, this is because valves and other conventional controlcomponents have packing glands, seals, and similar temperature sensitivecomponents which are not capable of withstanding the temperatures towhich such heat transfer media may be heated.

It will be apparent to those skilled in the arts'to which the presentinvention pertains that many structural modifications may be made in theexemplary embodiment of the present invention described above, ifdesired. For example, rectangular weir 104 may be relocated to thebottom of compartment 100 or replaced by weirs or openings of otherconfigurations. Similarly, openings of shapes other than rectangular maybe provided in bucket 118 of flow proportioning control 116 dependingupon the type of control desired.

Further, the flow proportioning control shown in FIG- URES lA and 1B maybe replaced with flow proportioning controls 133 (FIGURES 5 and 6) or134 (FIGURES 7 and 8), if desired. Referring rst to FIGURES 5 and 6,flow proportioning control 133 includes a transition member 136 fixed tothe discharge end of zone return conduit 114, a flow dividing member138, and a hydraulic or pneumatic motor 140. Transition lmember 136,which may be of any desired configuration, has an elongated slit 142through which the liuid returning through main zone return conduit 114is discharged. The fluid flowing through slit 142 is divided into twostreams by flow dividing member 138, one of the streams flowing intocompartment 100 and the other into the main body of liquid 102 instorage tank 88. By varying the ow volume of the fluid stream divertedinto compartment 100, the temperature of the liquid in the latter may beregulated in substantially the same manner as in the embodiment of theinvention de scribed previously.

The proportion of the kliuid diverted into compartment 100 is altered byrepositioning flow divider 138. This is accomplished by fixing flowdividing member 138 to a pivot rod 144 journalled in bearings 146 at theupper edge of zone compartment side wall 122. Pivot rod 144 is connectedthrough link 148 to the piston rod 150 of motor 149 which, whenoperated, moves the ow divider. The operation of motor 140 is regulatedby a controller such as that described above in conjunction with theembodiment of FIGURE 1.

In the llow proportioning control 134 illustrated in FIGURES 7 and 8, aweir box 152 is mounted below the discharge end of return conduit 114and above zone compartment side wall 122. Liquid flowing into weir box152 from return conduit 114 is discharged from the box through a weir154 in its side wall 156. A flow dividing vane 158, which may beidentical to the vane 138 described above, is positioned in the path ofthe liquid liowing through weir 154. Vane 158 divides this flow into twostreams, one of which is discharged into zone compartment 100 and theother of which is discharged into the main body of liquid 102 in storagetank 88. In this ernbodiment of the invention, liow dividing vane 158 isconnected through pivot pin 160 and link 162 to a vane-positioning motorin the same manner as in the embodiment of FIGURE 5. The modus operandiof this embodiment and the embodiment of FIGURES and 6 are substantiallyidentical.

As indicated above, the exemplary embodiment of the present inventionillustrated in FIGURE 1 alsor includes an auxiliary heating systemincluding a heating unit 92 for melting the solid heat transfer mediumwhen the system is started up. Since HTS must be heated to a temperatureof 288 F. to melt it, steam is preferably employed as a circulating heattransfer medium in this system. From heating unit 92, the steam flowsthrough supply conduit 164 into heating coils 166 disposed in the istorage tank 88 for the circulating medium. From the heating coils thesteam or other heat transfer lluid is returned to heating unit 92through a main return conduit 168. Heating coils 166 melt the main bodyof heat transfer medium 102 in tank 88.

To melt the heat transfer medium in the zone compartments 100, heatingcoils 170 are connected in parallel between supply and return conduits164 and 16S.

Also connected in parallel between main supply and return conduits 164and 168 are supply and return conduits 172 and 174, which connectauxiliary heating unit 91 with dryer 22. As shown in FIGURES 1B, 2, and3, conduits 172 and 174 supply the heat transfer medium to and return itfrom tubular fluid circulating members 176 fixed to the legs 64 of theradiant heaters 62 in heat exchange units 34 and 36. The conduits andfluid circulating members are connected through supply and returnheaders 178 and 180 and branch conduits 182, only part of which areshown.

When the installation is shut down, all of the HTS drains back into themain tank from the radiators which leaves them free of salt. Uponstart-up the steam owing through tubes 176 preheats the radiators to aternperature above the melting point of the salt so that when the saltis pumped into them it will not congeal.

When the system is shut down a cold liquid can be run through theauxiliary system described above to quickly reduce the temperature ofthe heat transfer liquid in the various components.

The invention may be embodied in other specic forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

What is claimed and desired to be secured by Letters Patent is:

1. A multiple Zone heating installation, comprising:

(a) storage means containing a body of heat transfer medium adapted tobe circulated in liquid form;

(b) means including a fluid heater and a first circulating systemcomprising a uid circulator and supply and return conduits connectingsaid fluid heater to said storage means for maintaining the body of heattransfer medium .in said storage means substantially at a giventemperature level;

(c) multizone heat using means;

(d) compartment means in said storage means for each of said zones, theinterior of each said compartment means being in iiuid communicationwith the main body of liquid in said storage means, whereby said liquidcan ow into said compartment means as liquid in said compartment meansis withdrawn therefrom;

(e) a circulation system comprising supply and return conduits and acirculator for supplying liquid from each said compartment means to theassociated zone of the heat using means and for returning the liquidthus supplied to said storage means; and

(f) independently adjustable, flow dividing means for dividing theliquid returned fro-m each said zone between the compartment means fromwhich the liquid was supplied and the main body of liquid in the storagemeans;

(g) whereby the liquid supplied to each said compartment means mayconstitute a mixture of relatively cool liquid returned from theassociated zone and relatively hot liquid from the main body of liquidin the storage means of different proportions and the temperature of theliquid in each said compartment means and available for supply to theassociated zone may therefore be independently regulated.

2. The multiple zone heating installation of claim 1, together with acontroller for positioning each of said flow dividing means to therebydetermine the proportioning of flow by said divider between the mainbody of liquid in the storage means and the compartment means with whichthe flow dividing mean is associated, each said controller having atemperature responsive sensor in the Zone of the heat using means withwhich the flow dividing means controlled thereby is associated.

3. The multiple zone heating installation of claim 1:

(a) wherein said heat transfer medium is a solid at nor- -mal ambienttemperatures; and

(b) including an auxiliary system for liquefying the heat transfermedium comprising heat exchangers adapted to have a heated duidcirculated therethrough so disposed in the storage means as to heat themain body of heat transfer medium therein and in each of saidcompartment means so as to heat the medium in the compartment, means forheating said uid, and Imeans including supply and return conduitsconnecting said fluid heating means to said heat exchangers.

4. The multiple zone heating system of claim 1, whe-rein each of saidcompartment means is thermally insulated from the main body of heattransfer medium in the storage means therefor.

5. A multiple zone heating system, comprising:

(a) storage means containing a heat transfer medium adapted to becirculated in liquid form;

(b) heating means for maintaining the main body of heat t-ransfer mediumin said storage means substanitally at a given temperature level;

(c) multizone heat using means;

(d) a separate compartment in said storage means for each zone of theheat using means from which the liquid supplied to said zone iswithdrawn;

(e) a system for circulating the heat transfer medium from thecompartments in the storage means to the zones of the heat using meanswith which they are associated; and

(f) means for regulating the temperature of the heat transfer liquidsupplied to each of said zones independently of the temperature in theother compartments and independently of the main body of liquid in thestorage means, said last-named means including, for each zone of theheat using means:

(1g) means operably associated with the compartment in the storage meansfor the zone for supplying relatively cool liquid -returned from thezone and relatively hot liquid from the main body of liquid in thestorage means to said compartment to maintain a body of liquid therein;and

(h) means for controlling the proportion of cool to hot liquid thussupplied to said compartment and thereby governing the temperature ofthe liquid in said compartment and available for supply to said zone.

6. The heating system of claim 5, wherein the temperature regulatingmeans associated with each of said zones comprises means on the supplyside of said circulation system for mixing rela-tively hot liquid fromthe liquid heating means with relatively cool liquid returned from thezone to thereby govern the temperature of the liquid available forsupply to the zone.

7. The heating system of claim 5:

(a) wherein said heat transfer means is a solid at normal ambienttemperatures; and

(b) including an auxiliary system independent of said heating means andhaving heat exchange means in said storage means for liquefying saidheat transfer medium during start-up of the heating system.

8. The heating system of claim 5, wherein said proportion controllingmeans comprises temperature sensing means in the zone and fluid-directing means operatively connected thereto `and capable of divertingvarying proportions of the returning fluid into said compartment tothereby regulate the proportion of returning fluid delivered to saidcompartment and therefore the proportion of cool to hot liquid as thetemperature detected by said sensing means changes, whereby thetemperature of the liquid in the compartment and available for supply tothe zone may be increased and decreased as the sensed temperaturechanges -to compensate for'changing heat demands in said zone.

9. The heating system of claim 5, together with:

(a) means for circulating the heat transfer medium between the storagemeans and the liquid heating means; and

(b) separate means operable independently of each other and of saidlast-mentioned circulating means for circulating said heat transfermedium to each said heating zone and for returning it to said storagemeans.

10. A multiple zone heating installation, comprising:

(a) storage means containing a body of heat transfer medium adapted tobe circulated in liquid form;

(b) means for maintaining the body of heat transfer medium in saidstorage means substantially at a given temperature level;

(c) multizone heat using means;

(d) compartment means for each of said zones, the interior of each saidcompartment means being in uid communication with the main body ofliquid in said storage means; whereby said liquid can flow into saidcompartment means as liquid in said compartment means is withdrawntherefrom;

(e) a circulation system for supplying liquid from each said compartmentmeans to the associated zone of the heat using means and for returningthe liquid thus supplied to said storage means; and

(f) independently adjustable means for dividing the liquid returned fromeach said zone between the compartment means from which the liquid wassupplied and the main body of liquid in the storage means;

(g) whereby the liquid supplied to each said compartment means mayconstitute a mixture of relatively cool liquid returned from theassociated zone and relatively hot liquid from the main body of liquidin the storage means of different proportions and the temperature of theliquid in each said compartment means and available for supply to theassociated zone may therefore be independently regulated.

References Cited UNITED STATES PATENTS 1,586,987 6/1926 Govers 126-3782,006,193 6/ 1935 Bell 237-56 2,153,382 4/ 1939 Martin 236-1 2,255,2929/ 1941 Lincoln. v 2,295,149 9/ 1942 Adams et al. 236-1 2,490,932 12/1949 Thuney 237-8 2,491,576 12/1949 Oaks 237-8 2,910,244 10/1959 Payne237-56 3,119,560 1/ 1964 Swaney 237-56 FOREIGN PATENTS 162,684 9/ 1933Switzerland.

EDWARD J. MICHAEL, Prz'mwy Examiner.

1. A MULTIPLE ZONE HEATING INSTALLATION, COMPRISING: (A) STORAGE MEANSCONTAINING A BODY OF HEAT TRANSFER MEDIUM ADAPTED TO CIRCULATED INLIQUID FORM; (B) MEANS INCLUDING A FLUID HEATER AND A FIRST CIRCULATINGSYSTEM COMPRISING A FLUID CIRCULATOR AND SUPPLY AND RETURN CONDUITSCONNECTING SAID FLUID HEATER TO SAID STORAGE MEANS FOR MAINTAINING THEBODY OF HEAT TRANSFER MEDIUM IN SAID STORAGE MEANS SUBSTANTIALLY AT AGIVEN TEMPERATURE LEVEL; (C) MULTIZONE HEAT USING MEANS; (D) COMPARTMENTMEANS IN SAID STORAGE MEANS FOR EACH OF SAID ZONES, THE INTERIOR OF EACHSAID COMPARTMENT MEANS BEING IN FLUID COMMUNICATION WITH THE MAIN BODYOF LIQUID IN SAID STORAGE MEANS, WHEREBY SAID LIQUID CAN FLOW INTO SAIDCOMPARTMENT MEANS AS LIQUID IN SAID COMPARTMENT MEANS IS WITHDRAWNTHEREFROM; (E) A CIRCULATION SYSTEM COMPRISING SUPPLY AND RETURNCONDUITS AND A CIRCULATOR FOR SUPPLYING LIQUID FROM EACH SAIDCOMPARTMENT MEANS TO THE ASSOCIATED ZONE OF THE HEAT USING MEANS AND FORRETURNING THE LIQUID THUS SUPPLIED TO SAID STORAGE MEANS; AND (F)INDEPENDENTLY ADJUSTABLE, FLOW DIVIDING MEANS FOR DIVIDING THE LIQUIDRETURNED FROM EACH SAID ZONE BETWEEN THE COMPARTMENT MEANS FROM WHICHTHE LIQUID WAS SUPPLIED AND THE MAIN BODY OF LIQUID IN THE STORAGEMEANS; (G) WHEREBY THE LIQUID SUPPLIED TO EACH SAID COMPARTMENT MEANSMAY CONSTITUTE A MIXTURE OF RELATIVELY COOL LIQUID RETURNED FROM THEASSOCIATED ZONE AND RELATIVELY HOT LIQUID FROM THE MAIN BODY OF LIQUIDIN THE STORAGE MEANS OF DIFFERENT PROPORTIONS AND THE TEMPERATURE OF THELIQUID IN EACH SAID COMPARTMENT MEANS AND AVAILABLE FOR SUPPLYING TO THEASSOCIATED ZONE MAY THEREFORE BE INDEPENDENTLY REGULATED.